Impurity-induced sub-gap bound gap states in alkali doped iron chalcogenide superconductors

Abstract

Measurements of the local density of states near impurities can be useful for identifying the superconducting gap structure in alkali doped iron chalcogenide superconductors K_xFe_{2-y}Se_2. Here, we study the effects of nonmagnetic and magnetic impurities within a nearest neighbor d-wave and next-nearest neighbor s-wave superconducting state. For both repulsive and attractive nonmagnetic impurities, it is shown that sub-gap bound states exist only for d-wave superconductors with the positions of these bound states depending rather sensitively on the electron doping level. Further, for such disorder Coulomb interactions can lead to local impurity-induced magnetism in the case of d-wave superconductivity. For magnetic impurities, both s-wave and d-wave superconducting states support sub-gap bound states. The above results can be explained by a simple analytic model that provides a semi-quantitative understanding of the variation of the impurity bound states energies as a function of impurity potential and chemical doping level.

8 pages, 7 figures

References in corpus (12)

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Cited by in corpus (4)

• On the Remarkable Superconductivity of FeSe and its Close Cousins
• Surface electronic structure and evidence of plain s-wave superconductivity in (Li0.8Fe0.2)OHFeSe
• Zero-energy bound states in the high-temperature superconductors at the two-dimensional limit
• Evolution of quasiparticle states with and without a Zn-impurity in doped 122 iron pnictides